A unit for a heating, ventilation, and air conditioning (HVAC) system, such as, but not limited to, a chiller unit, can include a lubricant. Depending upon a pressure differential in a compressor of the unit, a pressure differential above a threshold amount can cause a loss of lubricant through a lubricant tank vent conduit which provides a fluid connection between a lubricant tank assembly and an evaporator of the unit. The loss of lubricant to the evaporator can be at a greater rate than lubricant is returned from the evaporator lubricant return system.